It's floating independently at each exchange, coinbase could be in real bad shape since they guarantee 1:1 conversion.. you can buy on an exchange that allows it to float, xfer to coinbase and take advantage of their guarantee....

Coinbase could be left with a bag of devalued usdc, but... they just paused swaps, so they may continue to display $1 since no trades between dollars and usdc are actually occurring.

Gonna be interesting.